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Re: [PATCH] malloc: Run fork handler as late as possible [BZ #19431]
- From: "Tulio Magno Quites Machado Filho" <tuliom at linux dot vnet dot ibm dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Cc:
- Date: Tue, 10 May 2016 10:41:52 -0300
- Subject: Re: [PATCH] malloc: Run fork handler as late as possible [BZ #19431]
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Hi Florian,
Florian Weimer <fweimer@redhat.com> writes:
> 2016-04-13 Florian Weimer <fweimer@redhat.com>
>
> [BZ #19431]
> Run the malloc fork handler as late as possible to avoid deadlocks.
> * malloc/malloc-internal.h: New file.
> * malloc/malloc.c: Include it.
> * malloc/arena.c (ATFORK_MEM): Remove.
> (__malloc_fork_lock_parent): Rename from ptmalloc_lock_all.
> Update comment.
> (__malloc_fork_unlock_parent): Rename from ptmalloc_unlock_all.
> (__malloc_fork_unlock_child): Rename from ptmalloc_unlock_all2.
> Remove outdated comment.
> (ptmalloc_init): Do not call thread_atfork. Remove
> thread_atfork_static.
> * malloc/tst-malloc-fork-deadlock.c: New file.
> * Makefile (tests): Add tst-malloc-fork-deadlock.
> (tst-malloc-fork-deadlock): Link against libpthread.
> * manual/memory.texi (Aligned Memory Blocks): Update safety
> annotation comments.
> * sysdeps/nptl/fork.c (__libc_fork): Call
> __malloc_fork_lock_parent, __malloc_fork_unlock_parent,
> __malloc_fork_unlock_child.
> * sysdeps/mach/hurd/fork.c (__fork): Likewise.
Did you notice any intermittent on malloc/tst-mallocfork after this patch?
The child is getting into a deadlock if the signal arrives before the parent
is able to complete __malloc_fork_unlock_parent().
--
Tulio Magno